189:
20:
106:
437:. A ship designer can compare the length at the water line for a design with and without a bulb necessary to power the vessel at its operating speed. The higher the speed, the bigger the benefit of the bulbous bow in diminishing the necessity for a longer water line to achieve the same power requirement. Bulbs typically are v-shaped on the bottom to minimise slamming in rough seas.
394:
definitively studied by Thomas
Havelock, Cyril Wigley and Georg Weinblum, including Wigley's 1936 work "The Theory of the Bulbous Bow and its Practical Application" which examined the issues of wave production and damping. Inui's initial scientific papers on the effect of bulbous bow on wave-making resistance were collected into a report published by the
159:
deal of its time at a slow speed, the increase in drag will not be offset by the benefit in damping bow wave generation. As the wave counter effects are only significant at the vessel's higher range of speed, bulbous bows are not energy efficient when the vessel cruises outside of these ranges, specifically at lower speeds.
158:
The addition of a bulb to a ship's hull increases its overall wetted area. As wetted area increases, so does drag. At greater speeds and in larger vessels it is the bow wave that is the greatest force impeding the vessel's forward motion through the water. For a vessel that is small or spends a great
393:
during the 1950s and 1960s, independently of
Japanese naval research. Inui based his research on earlier findings by scientists made after Taylor discovered that ships fitted with a bulbous forefoot exhibited substantially lower drag characteristics than predicted. The bulbous bow concept was first
55:, and stability. Large ships with bulbous bows generally have twelve to fifteen percent better fuel efficiency than similar vessels without them. A bulbous bow also increases the buoyancy of the forward part and hence reduces the pitching of the ship to a small degree.
147:. While inducing another wave stream saps energy from the ship, cancelling out the second wave stream at the bow changes the pressure distribution along the hull, thereby reducing wave resistance. The effect that pressure distribution has on a surface is known as the
154:
A sharp bow on a conventional hull form would produce waves and low drag like a bulbous bow, but waves coming from the side would strike it harder. The blunt bulbous bow also produces higher pressure in a large region in front, making the bow wave start earlier.
402:
in 1962. It was eventually found that drag could be reduced by about five per cent. Experimentation and refinement slowly improved the geometry of bulbous bows, but they were not widely exploited until computer modelling techniques enabled researchers at the
432:
While the primary purpose of such bulbs is to reduce the power required to drive a vessel at its operating speed, their sea-keeping characteristics are also important. A ship's wave-making characteristics at its operating speed are reflected in its
143:. A bulb alone forces the water to flow up and over it forming a trough. Thus, if a bulb is added to a conventional bow at the proper position, the bulb trough coincides with the crest of the bow wave, and the two cancel out, reducing the vessel's
519:
62:, which is proportional to mass and the square of the velocity, benefit from having a bulbous bow that is designed for their operating speed; this includes vessels with high mass (e.g.
162:
Bulbous bows may be configured differently, according to the designed interaction between the bow wave and the countering wave from the bulb. Design parameters include:
109:
The combined influence of a subsurface bulb and a conventional bow on wave formation where the wave created by the bulb cancels that created by the conventional bow
729:
Seventeenth
Symposium on Naval Hydrodynamics: Wakes, Free Surface Effects, Boundary Layers and Viscous Flows, Two-phase Flow, Propeller/appendage/hull Interaction
23:
A "ram" bulbous bow curves upwards from the bottom, and has a "knuckle" if the top is higher than the juncture with the hullâthe through-tunnels in the side are
399:
306:
combining a bulbous forefoot with massive size and a redesigned hull shape. She was able to achieve speeds in excess of 30 knots (56 km/h).
293:
passenger liners launched in the late 1920s and early 1930s. Still, the idea was viewed as experimental by many shipbuilders and owners.
816:
474:
727:
879:
839:
767:
644:
345:
180:, when they are ballasted, by increasing the mass at a distance removed from the ship's longitudinal centre of gravity.
351:
800:
703:
654:
376:
226:, which entered service in 1910. The bow design did not initially enjoy wide acceptance, although it was used in the
591:
398:
in 1960. His work came to widespread attention with his paper "Wavemaking
Resistance of Ships" published by the
902:
404:
912:
726:
Grosenbaugh, M.A.; Yeung, R.W. (1989), "Non-linear bow flowsâAn experimental and theoretical investigation",
227:
323:, achieved equivalent speeds using traditional stem and hull design. However, a crucial difference was that
89:
Bulbous bows have been found to be most effective when used on vessels that meet the following conditions:
370:
364:
86:
that occur in those cases; examples include tugboats, powerboats, sailing vessels, and small yachts.
339:
310:
was famous for many things, including her clean entry into the water and markedly reduced bow wave.
693:
133:
616:
907:
357:
237:
434:
561:
536:
465:
In marine hydrodynamic applications, the Froude number is usually referenced with the notation
395:
338:. A modest bulbous bow was used in a number of their ship designs, including the light cruiser
335:
188:
917:
759:
356:. A far more radical bulbous bow design solution was incorporated into their massively large
289:
83:
863:
220:
193:
8:
390:
283:
207:
reduced resistance through the water before 1900. The bulbous bow concept is credited to
303:
212:
75:
875:
796:
773:
763:
733:
699:
650:
256:. They were referred to as Germany's North Atlantic greyhounds, two large commercial
44:
105:
19:
251:
245:
241:
846:
260:
that competed for the trans-Atlantic passenger trade. Both ships won the coveted
818:
Uncle Sam Enters The
Atlantic Race (article on the new construction in the 1930s)
268:
in 1929 with a crossing speed of 27.9 knots (51.7 km/h; 32.1 mph), and
216:
208:
177:
52:
327:
achieved these speeds with approximately thirty per cent less engine power than
166:
a) upward curvature (a "ram" bulb) versus straight forward (a "faired-in" bulb),
557:
318:
144:
67:
59:
48:
896:
737:
233:
777:
446:
244:. This lack of acceptance changed in the 1920s, with Germany's launching of
219:
and who used the concept (known as a bulbous forefoot) in his design of the
297:
24:
275:
The design began to be incorporated elsewhere, as seen in the U.S. built
261:
257:
79:
63:
199:
is visible on the left, while the vessel was under construction in 1925.
71:
36:
236:
to great success after the two ships of that class which survived the
871:
755:
277:
204:
148:
40:
132:
The effect of the bulbous bow can be explained using the concept of
793:
Record breakers of the North
Atlantic, Blue Riband Liners 1838-1952
140:
407:
to increase their performance to a practical level in the 1980s.
93:
The waterline length is longer than about 15 metres (49 ft).
43:. The flare or bulb modifies the way the water flows around the
732:, Washington, DC: Office of Naval Research, pp. 195â214,
389:
The modern bulbous bow was developed by Dr. Takao Inui at the
96:
The bulb design is optimised for the vessel's operating speed.
272:
surpassing her in 1930 with a crossing speed of 27.91 knots.
203:
Towing tests of warships had demonstrated that a below-water
415:
Bulbous bows embody the following defining characteristics:
672:
The Theory of the
Bulbous Bow and its Practical Application
211:, a naval architect who served as Chief Constructor of the
82:) have a reduced benefit from bulbous bows, because of the
514:{\displaystyle \mathrm {Fn} _{L}={\frac {u}{\sqrt {gL}}}}
556:
It is an important parameter with respect to the ship's
529:
is the relative flow velocity between the sea and ship,
334:
Bulbous bow designs were also developed and used by the
78:) and those that operate at slower speeds (less than 12
545:
is the length of the ship at the water line level, or
428:
Position of the shape's axis (e.g. forward or upwards)
477:
169:
b) bulb position with respect to the waterline, and
35:is a streamlined flaring or protruding bulb at the
691:
513:
646:Ship Design and Performance for Masters and Mates
894:
725:
614:
592:"What's The Importance Of Bulbous Bow Of Ships?"
400:Society of Naval Architects and Marine Engineers
752:U.S. Battleships: An Illustrated Design History
692:Bertram, Volker; Schneekluth, H. (1998-10-15).
589:
331:and a corresponding reduction in fuel use.
721:
719:
717:
715:
74:). Vessels of lower mass (less than 4,000
749:
560:, or resistance, especially in terms of
410:
187:
104:
18:
712:
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590:Chakraborty, Soumya (October 9, 2017).
125:Waterline and region of cancelled waves
100:
895:
862:
790:
695:Ship Design for Efficiency and Economy
669:
16:Protruding bulb at the front of a ship
784:
384:
139:A conventionally shaped bow causes a
687:
685:
683:
681:
638:
636:
585:
583:
581:
176:Bulbous bows also decrease a ship's
39:(or front) of a ship just below the
13:
821:. Popular Mechanics. February 1931
483:
480:
51:and thus increasing speed, range,
14:
929:
678:
633:
578:
317:s great rival, the British liner
122:Wave created by conventional bow
66:) or a high service speed (e.g.
856:
832:
615:Bray, Patrick J. (April 2005).
459:
192:The flaring bulbous bow of the
809:
743:
663:
608:
405:University of British Columbia
296:In 1935 the French superliner
183:
1:
828:– via books.google.com.
643:Barrass, Bryan (2004-07-09).
571:
870:. Cambridge, Massachusetts:
425:Length of forward projection
7:
537:acceleration due to gravity
440:
116:Profile of bow without bulb
10:
934:
750:Friedman, Norman (1985).
447:Axe bow § LEADGE-bow
375:and the aircraft carrier
452:
134:destructive interference
113:Profile of bow with bulb
791:Kludas, Arnold (2000).
670:Wigley, W.C.S. (1936).
363:battleships, including
238:Washington Naval Treaty
674:. Newcastle upon Tyne.
562:wave making resistance
515:
396:University of Michigan
336:Imperial Japanese Navy
200:
129:
28:
903:Watercraft components
864:Newman, John Nicholas
760:Naval Institute Press
535:is in particular the
516:
411:Design considerations
290:SS President Coolidge
191:
108:
22:
913:Nautical terminology
868:Marine hydrodynamics
554:in some notations.
475:
119:Wave created by bulb
101:Underlying principle
795:. London: Chatham.
469:and is defined as:
391:University of Tokyo
284:SS President Hoover
511:
385:Modern bulbous bow
344:and the carriers
304:Vladimir Yurkevich
240:were converted to
213:United States Navy
201:
130:
58:Vessels with high
29:
881:978-0-262-14026-3
769:978-0-87021-715-9
621:www.dieselduck.ca
509:
508:
419:Length-wise shape
242:aircraft carriers
925:
887:
885:
860:
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851:
845:. Archived from
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534:
528:
520:
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512:
510:
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497:
492:
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486:
468:
463:
316:
302:was designed by
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927:
926:
924:
923:
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893:
892:
891:
890:
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861:
857:
849:
842:
840:"Yamato Museum"
838:
837:
833:
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815:
814:
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803:
789:
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762:. p. 235.
748:
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413:
387:
314:
217:First World War
209:David W. Taylor
186:
178:pitching motion
172:c) bulb volume.
128:
103:
68:passenger ships
53:fuel efficiency
17:
12:
11:
5:
931:
921:
920:
915:
910:
908:Fluid dynamics
905:
889:
888:
880:
855:
852:on 2011-06-27.
831:
808:
801:
783:
768:
742:
711:
704:
677:
662:
655:
632:
617:"Bulbous bows"
607:
596:Marine Insight
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99:
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97:
94:
60:kinetic energy
15:
9:
6:
4:
3:
2:
930:
919:
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904:
901:
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802:1-86176-141-4
798:
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707:
705:9780080517100
701:
697:
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688:
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673:
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656:9780080454948
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505:
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470:
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458:
448:
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444:
438:
436:
435:Froude number
427:
424:
422:Cross-section
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397:
392:
382:
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234:battlecruiser
232:
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69:
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56:
54:
50:
46:
42:
38:
34:
26:
25:bow thrusters
21:
918:Interference
867:
858:
847:the original
834:
823:. Retrieved
817:
811:
792:
786:
758:, Maryland:
751:
745:
728:
698:. Elsevier.
694:
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665:
649:. Elsevier.
645:
624:. Retrieved
620:
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599:. Retrieved
595:
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541:
531:
525:
461:
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414:
388:
377:
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365:
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352:
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340:
333:
328:
324:
319:
311:
307:
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295:
288:
282:
276:
274:
269:
265:
258:ocean liners
252:
246:
228:
222:
202:
195:
175:
161:
157:
153:
138:
131:
88:
64:supertankers
57:
32:
30:
262:Blue Riband
215:during the
184:Development
149:form effect
72:cargo ships
47:, reducing
33:bulbous bow
897:Categories
825:2023-12-09
626:2023-12-09
601:2019-03-17
572:References
329:Queen Mary
320:Queen Mary
136:of waves:
872:MIT Press
756:Annapolis
738:0082-0849
325:Normandie
312:Normandie
308:Normandie
299:Normandie
278:SS Malolo
229:Lexington
221:USS
205:ram shape
196:Lexington
41:waterline
886:, p. 28.
866:(1977).
778:12214729
441:See also
223:Delaware
141:bow wave
378:Shinano
372:Musashi
347:ShÅkaku
878:
799:
776:
766:
736:
702:
653:
539:, and
523:where
366:Yamato
361:-class
359:Yamato
270:Europa
266:Bremen
253:Europa
247:Bremen
231:-class
84:eddies
70:, and
850:(PDF)
843:(PDF)
453:Notes
353:TaihÅ
341:Åyodo
315:'
876:ISBN
797:ISBN
774:OCLC
764:ISBN
734:ISSN
700:ISBN
651:ISBN
558:drag
350:and
287:and
250:and
194:USS
145:wake
49:drag
45:hull
80:kts
76:dwt
37:bow
899::
874:.
772:.
754:.
714:^
680:^
635:^
619:.
594:.
580:^
551:wl
467:Fn
381:.
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548:L
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494:=
489:L
484:n
481:F
27:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
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